1. Field of the Invention
The present invention relates generally to a magnetic tape recording/reproducing apparatus, and more particularly, to a digital audio tape recorder (hereinafter xe2x80x9cDATxe2x80x9d) streamer to be used as a large-capacity external memory back-up device for computers.
2. Description of the Related Art
The DAT streamer uses a DAT tape cassette, with recording to and reproduction from the magnetic tape carried out by a high-speed rotating drum, that is, a rotating head, the magnetic tape being driven between a capstan and a pinch roller. In the case of the DAT streamer, the recording of data to the magnetic tape involves reproducing the recorded location to verify the recording. Accordingly, the capstan repeatedly rotates in a counter-clockwise and a clockwise direction, with the magnetic tape also repeatedly running in both a forward and a reverse direction.
In the case of the DAT streamer, in order for the recording of data to and the reproduction of data from the magnetic tape to be performed reliably the reverse run of the magnetic tape must be as smooth as the forward run of the magnetic tape. That is, the height at which the magnetic tape runs in the reverse direction in the vicinity of the capstan must be the same as the height at which the magnetic tape runs in the forward direction.
FIGS. 1A, 1B and 1C show a conventional capstan tilt adjustment mechanism 10 in a magnetic tape recording/reproducing apparatus. Reference numeral 11 is the capstan, 12 is the pinch roller, 13 is a capstan motor, 14 is a capstan motor support plate and 15 is a chassis. The capstan 11 itself forms the spindle of the capstan motor 13. The capstan motor 13 is mounted on a bottom surface of the capstan motor support plate 14, with the capstan 11 protruding upward through the capstan motor support plate 14. The capstan motor support plate 14 is fixedly mounted on the chassis 15 at three separate locations indicated in the drawings as A, B and C. The pinch roller 12 is pressed against the capstan 11 in the direction of the arrow D, sandwiching the magnetic tape 16 therebetween. When the capstan 11 rotates in the counter-clockwise direction, the magnetic tape 16 runs forward in the direction of arrow F. When the capstan 11 rotates clockwise, the magnetic tape 16 runs backward in the direction of arrow R. The direction in which the tilt of the capstan 11 should be adjusted is indicated by the arrows G1 and G2.
Mounting position A comprises the capstan motor support plate 14 set on a top edge of a post 20 formed on the chassis 15, with a screw 21 screwed into the post 20 so as to fixedly mount the capstan motor support plate 14 in place. Mounting position B comprises a coil spring 23 fitted around a periphery of a post 22 formed on a top of the chassis 15, a hole of the capstan motor support plate 14 fitted to the post 22, and a screw 24 screwed into the post 22 from a top edge of the post 22. The capstan motor support plate 14 is lifted upward by the coil spring 23 against a bottom surface of a head portion of the screw 24. Mounting position C comprises a coil spring 26 fitted around a bolt 25 formed on the chassis 15, a hole of the capstan motor support plate 14 fitted to the bolt 25, and a nut 27 fastened to the bolt 25. The capstan motor support plate 14 is lifted upward by the coil spring 26 and pressed against a bottom surface of a head portion of the nut 27.
Line H is a line connecting mounting position A and mounting position B. Line I is a line passing through mounting location C and intersecting with line H.
Tightening the nut 27 causes mounting location C of the capstan motor support plate 14 to sink, the capstan motor support plate 14 to tilt about the line H and an edge of the capstan 11 to tilt toward mounting position C parallel to line I. Conversely, loosening the nut 27 causes mounting location C of the capstan motor support plate 14 to rise and the capstan 11 to tilt away from mounting position C parallel to line I. In this manner the tilt of the capstan 11 is adjusted and the reverse run of the magnetic tape made the same as the forward run of the magnetic tape.
However, the direction of the tilt of the capstan 11 may in some cases be changed by the force of the coil spring 23 because mounting location B supports the capstan motor support plate 14 by using a coil spring 23. If the force of the coil spring 23 is weak, then the capstan 11 will tilt in the direction shown in arrow J when the nut 27 is manipulated, and consequently the tilt of capstan 11 will deviate from the proper adjustment direction by an angle xcex8. As a result, it can become difficult to make the reverse run of the tape the same as the forward run of the tape.
It is possible to prevent the above-described problem from arising by increasing the strength of the force of the coil spring 23. However, doing so increases the strength of the mounting at mounting position B of the capstan motor support plate 14. As a result, when the nut 27 is turned the section of the capstan motor support plate 14 bends at mounting position B, changing the gap between the magnet and the coil of the capstan motor 13 and thus changing the torque of the capstan motor 13. A change in the torque of the capstan motor causes instability in the run of the magnetic tape.
Additionally, the capstan motor support plate 14 is susceptible to external vibrations because mounting location B supports the capstan motor support plate 14 by using a coil spring 23.
Accordingly, it is a general object of the present invention to provide an improved and useful magnetic tape recording/reproducing apparatus in which the problems described above are eliminated. Another and more specific object of the present invention is to provide a magnetic tape recording/reproducing apparatus in which the tilt of the capstan is adjusted smoothly.
The above-described objects of the present invention are achieved by a magnetic tape recording/reproducing apparatus comprising:
a pinch roller;
a capstan against which the pinch roller presses so as to drive a magnetic tape; and
a capstan tilt adjustment mechanism for adjusting the tilt of the capstan so that the magnetic tape runs substantially smoothly and without damage to the edges of the tape,
the capstan tilt adjustment mechanism comprising:
a support plate for rotatably supporting the capstan;
a first supporting part and a second supporting part for pivotally supporting the support plate with respect to a chassis at positions on both sides of the capstan so as to tilt the capstan in a direction which ensures that the magnetic tape runs substantially smoothly and without damage to the edges of the tape; and
an adjusting screw mechanism for pivoting the support plate with respect to the chassis,
both the first and second supporting parts having a structure that pivotally fixes the support plate at a predetermined height position above the chassis.
According to the invention described above, the first and second supporting parts have a structure that restricts movement of the support plate in the vertical direction, so the tilt of the capstan can be adjusted smoothly in the proper adjustment direction because the support plate does not tilt along the direction of the first and second supporting parts. Accordingly, it is possible to make the magnetic tape behave the same way when run in reverse as when the magnetic tape is run forward.
Moreover, the first and second supporting parts have a structure that restricts movement of the support plate in the vertical direction, so vibration of the capstan motor support plate is not amplified in the event that external vibrations are received and the capstan and an area thereabout acquire a vibration resistance superior to that of the conventional art.
Additionally, the above-described objects of the present invention are achieved by the magnetic tape recording/reproducing apparatus as described above, wherein the first and second supporting parts each comprise:
a substantially wedge-shaped supporting base portion formed on the chassis; and
a countersunk screw which passes through a hole in the support plate and screws into a hole in the supporting base portion and which mounts the support plate on the supporting base portion.
According to the invention described above, restrictive force exerted by the capstan motor support plate on the first and second supporting parts during its adjustment is small, so the pivotal displacement clockwise and counter-clockwise of the capstan motor support plate through the range of the small angle centered on line K does not unnecessarily bend the capstan motor support plate and, accordingly, the width of the air gap does not change. As a result, the characteristics of the capstan motor are not affected.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.